An Introduction to ADUs

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In September 2016, Governor Jerry Brown signed two separate accessory dwelling unit bills into state law. An Accessory Dwelling Unit (ADU), commonly referred to as “in-law suite” or “granny flat” are additional living spaces on properties zoned as single-family residences that have a separate kitchen, bathroom, and exterior access independent of the primary residence. AB 2299 and SB 1069 makes clear that local city ordinances which do not align with State law shall be “null and void” and that, until a local municipality adopts its own ordinance in accordance with State law, the State standards shall be enforced. In response, the Los Angeles Department of City Planning has prepared such an ordinance.

The ADU concept is fairly basic: having a second small dwelling right on the same grounds your regular single-family house, such as: an apartment over the garage, a garage conversion in the backyard or a basement apartment.

Regardless of its physical form, legally an ADU is part of the same property as the main home. It cannot be bought or sold separately, as a condominium or a dwelling on wheels might be. The owner of the ADU is the owner of the main home.

ADUs are a flexible type of housing unit because they allow for different uses, and serve different populations ranging from students and young professionals to people with disabilities and senior citizens. By design, ADUs are more affordable and can provide additional income to homeowners. A recent study noted that one unit of affordable housing costs about $500,000 to develop whereas an ADU can range anywhere up to $200,000 on the expensive end in high housing cost areas.

Local governments encourage the development of ADUs as they improve access to jobs, education and services for many California residents. Some key Provisions:

  • ADUs are only allowed in zones that allow residential uses with an existing single-family residence
  • ADUs are limited to only one per lot
  • ADUs are limited in size to 50% of the primary residence. Under no circumstance can an ADU be larger than 1,200 sq. ft. As for detached ADUs, the City may not require an ADU less than 640 sq. ft.
  • ADUs are required to meet all underlying zoning, floor area and land use regulations


  • Homeowners must add one parking spot if the garage is converted, but it can be located anywhere on the property, and it can also be in a driveway or tandem.
  • Parking spaces must be 8 ½ ft. X 18 ft. Compact parking is not allowed.
  • Parking is NOT required if you live within half a mile of public transit.
  • Parking is NOT required if you live in a historic district.
  • Parking is NOT required if the accessory dwelling unit is part of an existing primary residence. (For example, you are converting an existing basement or another part of your home).
  • Parking is NOT required if you live within one block of a car share. You can take a look at or for car share program maps.

Many lots in LA are within a half-mile of transit so that ADU parking will not be required. The City publishes a transit map here. Check to see if your lot appears to be within a half-mile radius of a bus stop, rail station, or a dedicated space where a shared-vehicle is parked.

Visit the LA Department of Building and Safety’s website to learn more at and then contact your favorite architect.

If you would like a list of local architect, contact Dan May at (310) 739-8647 or

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